Field of the Invention
The present embodiments herein relate to the field of high-performance environmentally-acceptable hydraulic fluid blend containing fluids from up to four different classes of environmentally-acceptable hydraulic fluids, plus additives.
Discussion of the Related Art
The purpose of a lubricant is generally to minimize friction and wear of metals. Lubricants generally consist of a base fluid and additives selected to improve the lubricating properties or other properties of the lubricant (e.g., stability, performance at low or high temperature, etc.). With industrialization, mineral based lubricants became important in the market. Most existing heavy duty lubricating oils used for construction equipment and the like contain mineral oils as a main a component. For example, hydraulic systems found in farm tractors, backhoes, excavators, garbage trucks, snow plows and other heavy equipment generally use mineral oil based fluids as lubricants. Mineral oils have the advantages of lubricity, longevity, and corrosion resistance.
The drawbacks of mineral based lubricants are that they are toxic, they have long term residual properties making them difficult to dispose of safely (i.e., long term, they have very low biodegradability), and they are very difficult to clean if there is an accidental spill. In particular, they are environmentally unacceptable. Thus, unauthorized release and spill of mineral oil based lubricants can have significant adverse impacts on terrestrial and aquatic environments, as well as underground sources of drinking water. Furthermore, scattering and leakage of oil is generally difficult to avoid during usage; hence, mineral oil usage inevitably leads to at least some contamination of the environment. Spillage clean up can require removing the top layer of the grass or soil and containment for proper disposal which involves significant labor hours and additional costs.
Accordingly, because of the foregoing problems with respect to mineral-oil derived hydraulic fluids, there is a desire in the industry for Environmentally-Acceptable (EA) hydraulic and lubricating fluids to protect the environment but still offer beneficial lubricating properties. Generally, there are four basic types of environmentally friendly hydraulic and lubricating fluids that are commonly used individually. Each have different chemistries and each are derived from different stocks and thus have different applications and thus may necessitate a designed composition to address lubricating a material (e.g., seals) that it is to interact with during particular operations.
In particular, one of the four of such fluids is a hydraulic environmental ester synthetic (HEES) fluid, which is a water-insoluble synthetic ester derived from either petroleum, animal oils, or vegetable (typically rapeseed) oil feedstocks. Petroleum-sourced HEES fluids combine an organic acid and alcohol, whereas vegetable sourced fluids combine a fatty acid and alcohol. A second of such fluids includes hydraulic environmental triglyceride (HETG), which are water insoluble triglycerides derived from vegetable or animal oils with soybean, sunflower, and rapeseed (Canola) being the most common sources, wherein they often can contain soluble thickeners to increase viscosity. A third of such fluids includes hydraulic environmental poly glycols (HEPG), which are often but not necessarily water-soluble (e.g., oil-soluble) polyalkylene glycols (PAG), polymers made from reacting alkylene-oxide monomers such as ethylene oxide, propylene glycol, or propylene oxide with glycol. The fourth basic type of environmentally friendly hydraulic and lubricating fluid includes hydraulic environmental polyalphaolefin and related products (HEPR) fluids, which are water-insoluble polyalphaoletins (PAO) and related hydrocarbon-based fluids. Such synthetic hydrocarbons are made by polymerizing alpha olefins to produce PAO.
With respect to illustrative but not exhaustive example properties of such fluids, HEES fluids have a broad viscosity range and have high thermal and oxidative stability and good fluidity at low temperatures. However, they hydrolyze in the presence of water. HETG fluids are highly biodegradable and nontoxic and are noncorrosive. However, high-temperature operation can cause undesired fast oxidation and aging, extreme thickening and gumming, and they are vulnerable to water effects, causing hydrolysis and increased acidity. HEPG fluids have been found to be incompatible with polyurethane seals, and pumps and motors often utilized in systems requiring lubricants. HEPR fluids have outstanding oxidation stability, corrosion protection, beneficial lubricity, desired aging characteristics, and good viscosity performance over a wide temperature range. Nonetheless, much like HEPG fluids, they have been found to be incompatible with many seal and gasket materials.
It is to be noted however, that while each of the above four basic environmentally acceptable fluids have beneficial properties (in addition of course to deleterious properties), none of them can compete with unacceptable environmental (i.e., mineral based) fluids in all performance categories and thus when utilized, often require special system design and maintenance considerations.
Accordingly, there is a need to provide environmentally-acceptable hydraulic fluid blends that addresses environmental and system performance/cost concerns. The embodiments herein address such a need by providing a novel high-performance environmentally-acceptable hydraulic fluid blend containing fluids from up to four of the different classes of environmentally-acceptable hydraulic fluids discussed above, plus additives. By selecting relative concentrations of such Environmentally-Acceptable (EA) fluids in a novel fashion, resultant desired performance properties acting in a synergistic way are optimized, making them competitive with non-Environmentally-Acceptable (EA) fluids.